Recently, in response to requirements for compactness of packages and high density of mounting packages, a package (semiconductor device) of a small size called CSP (chip size package) having BGA structure using a tape carrier facilitating high-density wiring has been proposed. Particularly, several kinds of packages equal in size to semiconductor chips have been developed. Among them, a micro-BGA package devised by TESSERA Company is noticed as a highly reliable semiconductor package.
Construction of majority of these semiconductor devices is of a style in which there is mounted a semiconductor chip of center-pad type, in which electrodes are formed to be arranged along the central line of the chip, on a silicon resin layer provided on one surface of a tape carrier having an opening. Electrode portions of the semiconductor chip, leads connected to solder balls formed on the tape carrier, and the opening of the tape carrier are embedded to be protected by insulative sealing material.
FIG. 1 and FIG. 2 show the structure of wiring pattern in a conventional tape carrier having insulative film 7 having device hole 10 formed at the center and via-holes 11, and plating power-feeding leads 13 to form gold electro-plating layer 14 on the wiring pattern of conductor layer 8 including leads 9 and lands 12. Below tape carrier 2, there is provided elastmer 3 for mounting a semiconductor chip. The outer ends of plating power-feeding leads 13 are cut off and removed by outside punching tools 17 or the like after gold electro-plating layer 14 is formed.
For the manufacture of the tape carrier, insulating film 7 made of polyimide or the like is punched to form device hole 10 and via-holes 11, then, the wiring pattern of conductive layer 8 of leads 9, lands 12 and power-feeding leads 13 are formed on insulating film 7 by way of photo-etching. Gold electro-plating layer 14 is provided on the wiring pattern, power-feeding leads 13 exposed outside is cut off and removed by means of outside punching tool 17. Thereafter, elastic body (elastomer) 3 is provided on conductor layer 8 so as not to be projected outward from the periphery of insulating film 7.
FIG. 3 shows the structure of a conventional semiconductor device of BGA type. FIG. 4 shows a plan view of the semiconductor device (from the side of solder ball side). FIG. 5 shows the bottom of the semiconductor device (semiconductor chip side).
The semiconductor device is provided with semiconductor chip 1, tape carrier 2, elastomer 3 fixing both of semiconductor chip 1 and tape carrier 2, sealant 5 for protecting electrode portion 4 of semiconductor chip 1, and solder ball 6 serving as electrode for the semiconductor device, in its structure.
Owing to the structure of this semiconductor device, semiconductor chip 1 is mounted and fixed on the side of elastomer 3 of the tape carrier, whereby electrode 4 of semiconductor chip 1 and lead 9 of the tape carrier are joined electrically. Further, electrode 4 of semiconductor chip 1 and lead 9, thus joined, and device hole 10 are sealed air-tight by insulating sealant 5. Then, solder ball 6 is placed on land 12 of the tape carrier, and at last, by cutting along piece-cutting line 21 (FIG. 2), the semiconductor device is completed.
In the conventional tape carrier, however, wiring pattern is expanded and it is not easy to form a high density wiring, because the power-feeding leads 13 are drawn for each lead 9. Thus, it is difficult to respond to requirements for compactness and increase in number of pins. Moreover, when a semiconductor device using a conventional tape carrier is subjected to PCT (pressure cooker test) to evaluate the humidity resistance after completion of the package, water permeates from the terminal surface of power lead 13 exposed to the outside of the package (FIG. 3) and reaches lead 9 connected to electrode portion 4 of the semiconductor chip, thereby corrosion occurs at electrode portion 4 of the semiconductor chip.